A tube-in-tube assembly, apparatus and system for integrated condensation and evaporation

Abstract

According to the present invention, a tube-in-tube assembly (1), an apparatus (21), a system (100) and a method for integrated condensation and evaporation is disclosed. The assembly have high chemical, mechanical and thermal stability. The assembly provides a large surface area for combined condensation and evaporation for Multi-stage Flash (MSF), Multi-Effect (ME), and Mechanical Vapor Recompression (MVR) systems. The apparatus comprises of a housing (5) arranged to secure at least two tube-in-tube assemblies (1a, 1b), each comprising an outer tube (2) and an inner tube (3), at least three tube sheets (17, 18, 19) positioned between the at least two tube-in-tube assemblies (1a, 1b), and a plurality of inlets and outlets. The tube-in-tube assembly is fabricated with high performance polymers reinforced with graphite.

Description

A TUBE-IN-TUBE ASSEMBLY, APPARATUS AND SYSTEM FOR INTEGRATED CONDENSATION AND EVAPORATION

[0001] In general, the present disclosure relates to an assembly for treating industrial wastewater. More specifically, the present disclosure relates to a tube-in-tube assembly for integrated condensation and evaporation for Multi-stage Flash (MSF), Multi-Effect (ME), and Mechanical Vapor Recompression (MVR) systems.BACKGROUND

[0002] Industrial wastewater often exhibits extremely high or very low pH values, making it either acidic or alkaline, often contains chlorine ions that contribute to its corrosiveness. Without treatment, this wastewater poses a significant environmental treat.

[0003] Due to the extreme pH values and aggressive salt mixtures present in the wastewater / solution, materials like steel and titanium are unsuitable for condensation-evaporation processes. Instead, specialized equipment made from materials such as glass or graphite is required, which are both complex and expensive to manufacture.

[0004] Polymers like polyethylene (PE) and polypropylene (PP) offer a potential solution due to their ease of processing and inexpensive nature. However, these polymers have limitations, including low temperature resistance, poor mechanical strength, and low thermal conductivity, with a maximum operating temperature of less than 90°C.

[0005] Adequate heat conduction in standard polymers such as PE and PP can be achieved if the heat transfer surface is made as thin as possible, ideally between 20 and 100 micrometers. However, thinner surfaces compromise on mechanical stability.

[0006] Currently, solutions with a high salt concentration can only be concentrated through evaporation, an energy-intensive process. Thus, it is crucial to utilize the available energy as efficiently as possible.

[0007] Multi-stage processes like Multi-stage Flash (MSF), Multi-Effect (ME), and Mechanical Vapor Recompression (MVR) maximize energy utilization by recycling the input energy. The effectiveness of MSF and ME processes increases with a larger temperature difference between the heating and cooling stages.

[0008] Many salt solutions exhibit a significant increase in boiling point, which reduces the available temperature difference available for the process.

[0009] Using standard polymers like PP, even when compounded graphite, limits the upper operating temperature to 85°C. The cooling stages of the processes often faces constraints due to the cooling limitations of cooling towers, particularly in India where temperatures frequently do not drop below 35°C. Consequently, the maximum temperature difference (MTD) available for a multi-stage process is 50 K (Kelvin), calculated as 85°C minus 35°C.

[0010] For example, concentrating sulfuric acid from 15% to 50% significantly raises the boiling point. In a forced circulation multi-effect process, this increase in boiling point allows for only a one-stage or at most a two-stage heat recovery process. Therefore, enlarging the MTD is necessary.

[0011] When water is heated above 100°C, its vapor pressure increases, necessitating an increase in pressure to prevent boiling. This applies to both salt solutions and water-acid mixtures. For instance, water at 170°C has a vapor pressure of 7.92 bar.

[0012] The combination of high temperature (170°C) and high pressure (7.92) presents substantial challenges for the mechanical stability of the apparatus and the overall system.

[0013] In the multi-effect condensation and evaporation process, the volume flow of the solution to be concentrated is relatively small. For instance, starting with a volume flow of 1000 liters per hour and achieving a concentration of 75%, only 250 liters per hour remain as concentrate at the end. These low volume flows must be distributed as evenly as possible over the condensation and evaporation surfaces.

[0014] A simplified calculation for this scenario, assuming three effects, requires vaporizing 250 Kg per hour per effect, which must then be condensed in the subsequent effect. If 0.63 KWh of energy is released during condensation, a power of 157.5 KW must be transferred, with a logarithmic temperature difference of 5K when using high performance polymers like Polyphenylene sulfide (PPS) filled with Graphite (PPS-Gr) or polypropylene (PP) filled with Graphite (PP-Gr) and a k-value of 1000 W / m²K, an exchange surface of 31 m² is required. This means 1000 l per hour of solution must be evenly distributed over 37.5 m², corresponding to 26.66 l / m²h in effect 1. In effect 3, 500 liters per hour must be distributed, corresponding to 12.33 l / m²h. With such low volume flow across the heat exchange surface (HES) from top to bottom, the falling film of solution will not cover the entire HES, resulting in dry spots. Scaling and crystallization will occur at the solution / concentrate interface. In practice, this is avoided in falling film evaporators by forcing recirculation of the solution. However, this recirculation flow can significantly increase the electrical energy requirement of the evaporator.

[0015] Thus, there remains a need in the art to develop a tube-in-tube assembly with high chemical, mechanical and thermal stability for integrated condensation and evaporation during the treatment of industrial wastewater.OBJECT OF THE INVENTION

[0016] It is the primary object of the present disclosure to provide an energy efficient tube-in-tube assembly for an integrated condensation and evaporation unit / apparatus.

[0017] It is another object of the present disclosure to provide an apparatus with a large surface area for integrated condensation and evaporation for Multi-stage Flash (MSF), Multi-Effect (ME), and Mechanical Vapor Recompression (MVR) systems.

[0018] It is another object of the present disclosure to provide an energy efficient system for integrated condensation and evaporation.

[0019] It is another object of the present disclosure to provide a method for integrated condensation and evaporation for transporting particles in the solution upto several millimetres in size through the process.

[0020] In an aspect of the present disclosure, a tube-in-tube assembly for an integrated condensation and evaporation unit is disclosed. The tube-in-tube assembly comprises an outer tube and an inner tube. Further a portion of the inner tube is concentrically positioned within a portion of the outer tube along a vertical axis of the outer tube thereby forming a concentric annular gap between the inner surface of the outer tube and an outer surface of the inner tube. The tube in tube assembly has high chemical, mechanical and thermal stability. The assembly provides a large surface area for condensation and evaporation.

[0021] In another aspect of the present disclosure, an apparatus for integrated condensation and evaporation is disclosed. The apparatus comprises of a housing, at least three tube sheets and a plurality of inlets and outlets. The housing is arranged to secure at least two tube-in-tube assemblies, each comprising an outer tube and an inner tube. The at least three tube sheets are positioned between the at least two tube-in-tube assemblies. Further a portion of the inner tube is concentrically positioned within a portion of the outer tube along a vertical axis of the outer tube thereby forming a concentric annular gap between the inner surface of the outer tube and an outer surface of the inner tube. In yet another aspect of the present disclosure, a system for integrated condensation and evaporation is disclosed. The system comprises at least two apparatuses. The at least two apparatuses are connected in series via at least one connecting pipe, configured to transfer a vapour, a distillate and a concentrate from one apparatus to another. Each apparatus comprises a housing, at least three tube sheets and a plurality of inlets and outlets. The housing is arranged to secure at least two tube-in-tube assemblies, each comprising an outer tube and an inner tube. The at least three tube sheets are positioned between the at least two tube-in-tube assemblies. Further a portion of the inner tube is concentrically positioned within a portion of the outer tube along a vertical axis of the outer tube thereby forming a concentric annular gap between the inner surface of the outer tube and an outer surface of the inner tube.

[0022] In another aspect of the present disclosure, a method for integrated condensation and evaporation is disclosed. The method comprises the steps of passing a first vapor in a first apparatus through at least one tube in tube assembly at a vapor inlet, into an interior of a long cylindrical part of a housing followed by condensing the first vapor on the outer surface of an outer tube and forming a distillate. Then transferring the condensation energy released by condensation of the first vapor through the outer surface of the outer tube to the distillate flowing downwards. Passing a concentrate through a concentric annular gap at positions C and D and the concentrate enters the concentric annular gap at position E. Then flashing the concentrate through the lower pressure in the concentric annular gap, subsequently flowing of concentrate through the throttle followed by passing a feed mixture of a second vapor and concentrate upward into the tubes with the larger diameter within the annular gap at the position E between the outer tube and inner tube, wherein the feed mixture flashes due to the transferred condensation energy and lower absolute pressure in the annular gap and inside the first end cap. Followed by separating the second vapor and concentrate at the upper end G of the concentric annular gap. The concentrate flows downward in the interior of the inner tube at position G due to gravity and lower pressure in the interior of the inner tube. The concentrate flows into the inner volume of the lower end cap at the lower end of the inner tube. Then the concentrate flows out of the lower end cap at position H through the outlet opening to the next effect or to the concentrate tank.

[0023] The vapor flows from the top of the tubes with the larger diameter into the interior of the upper end cap. From the upper end cap, the vapor flows through the outlet opening into the second apparatus or next effect or to the final condenser.

[0024] At very low flow velocities in the annular gap, the Reynolds number is low, i.e. the flow is laminar and the heat transfer from the inner surface of the outer tube to the concentrate is low, particularly in the single-phase flow range. Here the heat transfer takes place by condensation on the outer wall of the tube with the larger diameter, heat conduction through the tube wall and subsequent heat conduction from the inner wall of the tube to the liquid concentrate.

[0025] From the height in the concentric gap at which the concentrate begins to boil, the heat transfer increases considerably. The heat transfer takes place from the inner wall of the tube to a two-phase mixture of concentrate and vapor, through the evaporation takes place on the inner wall of the tube.

[0026] In an alternate mode of operation, to increase the flow velocity, part of the concentrate is recirculated with a pump from the interior of the lower end cap into the concentrate flowing into the apparatus, for increasing the heat transfer in the area where the concentrate is liquid.

[0027] The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and modules.

[0028] illustrates a tube-in-tube assembly for an integrated apparatus for simultaneous condensation and evaporation in accordance with an exemplary embodiment of the present disclosure.

[0029] illustrates a top view of the concentric annular gap between the outer tube and the inner tube, in accordance with an exemplary embodiment of the present disclosure.

[0030] illustrates a three-dimensional view of the outer tube and the inner tube, in accordance with an embodiment of the present disclosure.

[0031] illustrates a sectional view depicting the integration of the tube-in-tube assembly within the integrated condensation and evaporation unit / apparatus, in accordance with an embodiment of the present disclosure.

[0032] illustrates a schematic representation of a system for integrated condensation and evaporation, in accordance with an embodiment of the present disclosure.

[0033] illustrates a multi effect system comprising a vapor generator, a distillate tank, a concentrate tank, in accordance with an embodiment of the present disclosure.

[0034] illustrates a multi effect system, in accordance with another embodiment of the present disclosure.

[0035] illustrates an apparatus with two sets of tube-in-tube assembly for integrated condensation and evaporation, in accordance with an embodiment of the present disclosure.

[0036] illustrates the cross-sectional view of rotationally symmetrical grommets, in accordance with an embodiment of the present disclosure.DETAILED DESCRIPTION OF THE INVENTION

[0037] The invention will be described in detail below with reference to the drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation procedures are given, but the scope of protection of the present invention is not limited to the following embodiments.

[0038] According to an exemplary embodiment of the present disclosure, a tube in tube assembly for an integrated condensation and evaporation unit / apparatus is disclosed. The tube in tube assembly has a high chemical, mechanical and thermal stability. The assembly provides a large surface area for combined condensation and evaporation for Multi-stage Flash (MSF), Multi-Effect (ME), and Mechanical Vapor Recompression (MVR) systems. In the embodiment of the present disclosure, the tube-in-tube assembly for the integrated condensation and evaporation apparatus requires little or no pre-treatment of the solution in terms of filtration and dosing of chemicals, e.g. anti-scalants.

[0039] In an embodiment of the present disclosure, the tube-in-tube assembly for the integrated condensation and evaporation apparatus directs three streams: incoming vapor, the solution to be concentrated and the newly generated vapor in one housing. Further the assembly transports particles / emerging crystals with the solution.

[0040] Referring to, illustrates a tube in tube assembly (1) for an integrated condensation and evaporation apparatus in accordance with an exemplary embodiment of the present disclosure. The assembly (1) comprises an outer tube (2) and an inner tube (3) with different outer and inner diameters. A portion of the inner tube (3) is concentrically positioned within a portion of the outer tube (2) along a vertical axis of the outer tube (2) thereby forming a concentric annular gap (4) between an inner surface of the outer tube (2) and an outer surface of the inner tube (3). The tubes (2, 3) are installed vertically for use in Multi-Effect (ME) process. The tubes (2,3) are arranged vertically position bottom B and position top T. The inner tube (3) is shorter at the position top T than the outer tube (2) and longer at the position bottom B than the outer tube (2).

[0041] Referring to, illustrates a top view of the concentric annular gap (4) between the outer tube (2), inner diameter and the inner tube (3), outer diameter, in accordance with an embodiment of the present invention. In an embodiment of the present disclosure, the inner diameter of the outer tube (2) is larger than the outside diameter of the inner tube (3). The inner diameter of the outer tube (2) is in the range of 10mm to 60mm. The outer diameter of the inner tube (3) is in the range of 8 mm to 58 mm, in particular in the range of 10 mm to 55 mm. The inner tube (3) and outer tube (2) are arranged around the same vertical axis resulting in a concentric annular gap (4) for the flow of concentrate (7). The difference in the radii of the concentric annular gap (4) is in the range of 1 mm to 10 mm, in particular in the range of 2 mm to 7 mm.

[0042] Referring to, illustrates a three-dimensional view of the outer tube (2) and the inner tube (3), in accordance with an embodiment of the present invention.illustrates the upper end of the shorter inner tube (3). For better visibility part of the outer tube (2) is removed.

[0043] In an embodiment of the present disclosure, the outer tube (2) is fabricated with a high thermal conductivity material selected from one of polymer Polyvinylenesulphide (PPS) filled with graphite (Gr) in the range of 55% to 85% by mass, polymer Polypropylene (PP) filled with graphite (Gr) in the range of 50% to 85 % by mass.

[0044] In an embodiment of the present disclosure, the outer tube (2) is fabricated with the polymer Polyvinylenesulphide (PPS) filled with graphite (Gr) is resistant to continuous temperature in the range 90°C to 200°C. The thermal conductivity of the outer tube fabricated with PPS-Gr is 5 to 8 W / mK perpendicular to the heat exchange surface, through plane.

[0045] In an embodiment of the present disclosure, the outer tube (2) is fabricated with the polymer Polypropylene (PP) filled with graphite (Gr) is resistant to continuous temperature in the range 1 to 100°C.

[0046] In an embodiment of the present disclosure, the inner tube (3) is fabricated with a low thermal conductivity material selected from a group comprising of unfilled polymers Polyvinylenesulphide (PPS), Polypropylene (PP). The materials Polyvinylenesulphide (PPS) or Polypropylene (PP) is filled with glass fibre for increasing the mechanical strength of the inner tube (3).

[0047] In an embodiment of the present disclosure, the outer tube (2) and the inner tube (3) are arranged vertically and are positioned differently in relation to each other along their lengths. The outer tube (2) is vertically longer than the inner tube (3) at the top, the inner tube (3) is vertically longer than the outer tube (2) at the bottom. The length of the outer tube is in the range of 1000mm to 3000mm, in particular in the range of 1500mm to 2500mm.

[0048] In an embodiment of the present disclosure, the length of the inner tube is in the range of 1000mm to 3000mm, in particular in the range of 1300mm to 2300mm. A shorter inner tube results in a greater distance between the upper edge of the outer tube and the inner tube, thereby reducing the risk of droplets carried along with the vapour entering the volume of the upper end cap during the process of boiling.

[0049] In an embodiment of the present disclosure, the outer tube (2) comprises of a plurality of fins in the axial direction for better heat transfer.

[0050] In an embodiment of the present disclosure, the inner tube (3) comprises of a plurality of positioning aids for maintaining the concentric annular gap (4) between the outer tube (2) and the inner tube (3) during the process of boiling.

[0051] Referring to, illustrates a sectional view depicting the integration of the tube-in-tube assembly within the integrated condensation and evaporation unit / apparatus, in accordance with an embodiment of the present disclosure. Referring to, a first vapor 6 flowing from an upstream flash chamber or effect flows to the outer surface 12 of the outer tube 2. The first vapor 6 condenses on the outer surface 12 of the outer tube 2 and forms the distillate 13. The distillate 13 flows downwards on the outer surface 12 of the outer tube 2 and collects on the upper surface 14 of the second tube sheet 18 in vertical direction from the top.

[0052] The absolute pressure p1 of the concentrate 7 upstream of the throttle 8 is higher than the absolute pressure p2 of the concentrate 7 downstream of the throttle 8. Concentrate 7 from the upstream flash chamber or effect flows to the concentric annular gap 4 in positions C and D. The concentrate 7 enters the concentric annular gap at position E. The concentrate 7 flashes through the lower pressure in the concentric annular gap 4, subsequent to flowing of concentrate 7 through the throttle 8. A mixture of a second vapor 9 bubbles and concentrate 7 flows upwards in the concentric annular gap 4. The newly generated second vapor 9 and concentrate 7 separates at the upper end G of the concentric annular gap 4. Further a new vapor 10 flows upwards and leaves the outer tube 2 at position F. The concentrate 7 is further concentrated subsequent to the flash and the vapor release. The concentrate 7 enters the interior of the inner tube 3 at position G, flows downwards through the interior 10 of the inner tube 3. The flow of the concentrate 7 is induced by gravity and lower absolute pressure in the subsequent effect. The concentrate 7 flows out of the inner tube 3 at the bottom at position H and then flows in an axial direction in the inner volume 11 of the lower end cap 12.

[0053] In another embodiment of the present disclosure, a method for integrated condensation and evaporation is disclosed. The method comprises the steps of passing a first vapor (6) in a first apparatus (21) through at least one tube in tube assembly (1) at a vapor inlet, into an interior of a long cylindrical part (15) of a housing (5) followed by condensing the first vapor (6) on the outer surface (12) of an outer tube (2) and forming a distillate (13). Then transferring the condensation energy released by condensation of the first vapor (6) through the outer surface (12) of the outer tube (2) to the distillate (13) flowing downwards. Followed by collecting the distillate (13) on the upper surface (14) of the second tube sheet (18) in a vertical direction from the top of the tube in tube assembly (1). Passing a concentrate (7) through a concentric annular gap at positions C and D and the concentrate (7) enters the concentric annular gap (4) at position and then flashing the concentrate (7) through the lower pressure in the concentric annular gap (4), subsequently flowing of concentrate (7) through the throttle (8). passing a feed mixture of a second vapor (9) and concentrate (7) upward into the tubes (2, 3) with the larger diameter within the annular gap (4) at the position E between the outer tube (2) and inner tube (3), whereby the feed mixture flashes due to the transferred condensation energy and lower absolute pressure in the annular gap (4) and inside the first end cap (16)In an embodiment of the present disclosure, the method further comprises the steps of separating the second vapor (9) and concentrate (7) at the upper end G of the concentric annular gap (4), whereby the concentrate flows downward in the interior (10) of the inner tube (3) at position G due to gravity and lower pressure in the interior (10) of the inner tube (3). The concentrate (7) flows into the inner volume of the lower end cap (20) at the lower end of the inner tube (3). The concentrate flows out of the lower end cap (20) through the outlet opening to the next effect or to the concentrate tank (29).

[0054] The vapor (9) flows from the top of the outer tubes (2) with the larger diameter into the interior of the upper end cap (16) . From the upper end cap (20) , the vapor (9) flows through the outlet opening into the second apparatus (22) / next effect (22) or to the final condenser.

[0055] At very low flow velocities in the concentric annular gap (4), the Reynolds number is low, i.e. the flow is laminar and the heat transfer from the inner surface of the outer tube (2) to the concentrate is low, particularly in the single-phase flow range. Here the heat transfer takes place by condensation on the outer wall of the outer tube (2) with the larger diameter, heat conduction through the outer tube wall and subsequent heat conduction from the inner wall of the tube (2) to the liquid concentrate (7).

[0056] From the height in the concentric annular gap (4) at which the concentrate (7) begins to boil, the heat transfer increases considerably. The heat transfer takes place from the inner wall of the tube (2) to a two-phase mixture of concentrate (7) and vapor (9), through the evaporation takes place on the inner wall of the tube (2).

[0057] In an alternate mode of operation, to increase the flow velocity part of the concentrate (7) is recirculated with a pump from the interior of the lower end cap (20) into the concentrate (7) flowing into the apparatus (21, 22), for increasing the heat transfer in the area where the concentrate (7) is liquid.

[0058] Referring to, illustrates a schematic representation of a system (100) for integrated condensation an evaporation. The system (100) comprises at least two apparatuses (21, 22). The at least two apparatuses (21, 22) are connected in series via at least one connecting pipe (24, 25, 27), configured to transfer a vapour (6, 9), a distillate (13) and a concentrate (7) from one apparatus to another. Each apparatus (21, 22) comprises a housing (5), at least three tube sheets (17, 18, 19) and a plurality of inlets and outlets. The housing (5) is arranged to secure at least two tube-in-tube assemblies (1a, 1b), each comprising an outer tube (2) and an inner tube (3). The at least three tube sheets (17, 18, 19) are positioned between the at least two tube-in-tube assemblies (1a, 1b). Further a portion of the inner tube (3) is concentrically positioned within a portion of the outer tube (2) along a vertical axis of the outer tube (2) thereby forming a concentric annular gap (4) between the inner surface of the outer tube (2) and an outer surface of the inner tube (3).

[0059] illustrates two successive effects / apparatus (21, 22) of the integrated condenser-evaporator multi-effect system (100), in accordance with an embodiment of the present disclosure. Effect / apparatus (21) is at a higher temperature and pressure than the effect / apparatus (22), which follows the flow direction of vapor (6, 9), distillate (13), and concentrate (7). Effects / apparatuses (21) and (22) illustrates three tube in tube assemblies (1a, 1b, 1c) and each effect (21,22) comprises three flows: vapor, concentrate and distillate.

[0060] A first vapor 6 flowing from an upstream flash chamber or effect flows to the outer surface 12 of the outer tube 2. The first vapor 6 condenses on the outer surface 12 of the outer tube 2 and forms the distillate 13. The distillate 13 flows downwards on the outer surface 12 of the outer tube 2 and collects on the upper surface 14 of the second tube sheet 18 in vertical direction from the top.

[0061] In position J, the concentrate 7 flows into volume 23 limited at the top by the central tube sheet 18 and at the bottom by the lower tube sheet 19. The concentrate 7 flows upwards in the concentric annular gap 4, subsequent to the decrease in absolute pressure in the concentric annular gap 4 during the flow from bottom to top. The condensation of the vapor 6 on the outer surface 12 of the outer tube 2 boils the concentrate 7 and a new second vapor 9 is formed. The concentrate 7 is further concentrated by the boiling process and the vapour release. The concentrate 7 flows downwards via the interior of the inner tube 3 into the inner volume 23 of the lower end cap 20. The newly generated second vapor 9 flows into the effect 22 through a connecting pipe 24. The above disclosed process takes place in effect 22 with second vapor 9 as with first vapor 6 in effect 21. The distillate 13 is collected on the surface 14 of the central tube sheet 18 and flows into effect 22 through the distillate connecting pipe 25 due to the lower pressure p in effect 22.

[0062] The distillate 13 in effect 21 is at saturation vapor pressure and temperature corresponding to the pressure p1, flows through throttle 26 into effect 22 and boils. After undergoing through boiling process, the distillate 13 has a lower saturation vapor pressure and a correspondingly lower temperature, due to lower absolute pressure in effect 22. The Non-condensable Gas (NCG) flows with the distillate 13 from effect 21 to effect 22.

[0063] The concentrate 7 flows from effect 21 to effect 22 through the concentrate connecting pipe 27. The concentrate 7 in effect 21 is at saturation vapor pressure and temperature corresponding to the pressure p1. The concentrate 7 boils downstream of the throttle 28 corresponding to absolute pressure p2 in effect 22. The resulting concentrate attains a new lower saturation vapor pressure and temperature.

[0064] In an exemplary embodiment of the present disclosure, a plurality of effects thermodynamically similar to effects 21 / 22 can be added to the effects 21 and 22.

[0065] Referring to, illustrates a multi effect system comprising a vapor generator 28, the effects 21 and 22, a distillate tank 30, a concentrate tank 29, in accordance with an embodiment of the present disclosure.further illustrates a final condenser 33, condensing the third vapor 34. The multi effect system illustrated indepicts only one tube in tube assembly / arrangement per effect. The flow of concentrate 7 is illustrated with dotted lines.

[0066] Referring to, illustrates a multi effect system, in accordance with another embodiment of the present disclosure.illustrates a simplified representation of a multi effect system, wherein the concentrate 7 is pumped from the lower absolute pressure and temperature of effect 22 to effect 21 at a higher temperature and absolute pressure with the aid of pump 31. This is helpful if the solubility of the solution to be concentrated increases with higher temperature, as is the case with FeCl2 dissolved in water, for example. The pump 32 feeds the concentrate 7 into the concentrate tank 29.

[0067] Referring to, illustrates an effect / apparatus 21 comprising two sets of tube-in-tube assembly for integrated condensation and evaporation, in accordance with an embodiment of the present disclosure. The apparatus (21) comprises of a housing (5), at least three tube sheets (17, 18, 19) and a plurality of inlets and outlets. The housing (5) is arranged to secure at least two tube-in-tube assemblies (1a, 1b), each comprising an outer tube (2) and an inner tube (3). The at least three tube sheets (17, 18, 19) are positioned between the at least two tube-in-tube assemblies (1a, 1b). Further a portion of the inner tube (3) is concentrically positioned within a portion of the outer tube (2) along a vertical axis of the outer tube (2) thereby forming a concentric annular gap (4) between the inner surface of the outer tube (2) and an outer surface of the inner tube (3).

[0068] In an embodiment of the present disclosure, the plurality of the inlets comprises of feed inlet, vapour inlet and distillate inlet. The plurality of outlets comprises of feed outlet, vapour outlet and distillate outlet. A continuous flow of non-condensable gases (NCGs) is maintained through the distillate inlet and outlet ports.

[0069] In an embodiment of the present disclosure, the inner part of the apparatus (21) is constructed vertically from bottom to top. The first tube sheet (17) and a second tube sheet (18) are separated by a short distance. The second tube sheet (18) and the third tube sheet (19) is separated by a greater distance. The tube in tube assembly extends from the first tube sheet (17) to the third tube sheet (19).

[0070] In an embodiment of the present disclosure, the housing (5) comprises a vertical section from bottom to top. The vertical section of the housing (5) comprises a first end cap (16), a short cylindrical part (35), a long cylindrical part (15) and a second end cap (20).

[0071] In an embodiment of the present disclosure, the first end cap (16), the second end cap (20), the short cylindrical part (35) and the long cylindrical part (15), each comprises at least one flange.

[0072] In an embodiment of the present disclosure, the housing (5) is fabricated with a material selected from glass fiber reinforced Polyvinylenesulphide (PPS), glass fiber reinforced Polypropylene (PP), steel that is protected against corrosion on the inside with a layer of plastic, enamel.

[0073] In an embodiment of the present disclosure, the atleast three tube sheets (17, 18, 19) are fabricated with high performance polymer Polyvinylenesulphide (PPS) filled with glass fiber in a range of 40% to 85% by weight, if the unit is operated at operating temperatures above 85°C.

[0074] In another embodiment of the present disclosure, the atleast three tube sheets (17, 18, 19) are fabricated with high performance polymer PP filled with glass fiber in a range of 40% to 85% by weight, if the unit is operated at operating temperatures below 85°C.

[0075] In an embodiment of the present disclosure, the outer walls of the housing (5) are sealed to the atleast three tube sheets (17, 18, 19) through a non-detachable sealing method selected from sealing with ultrasonic, glued into the atleast three tube sheets (17, 18, 19).

[0076] In another embodiment of the present disclosure, the atleast three tube sheets (17, 18, 19) are installed between the flanges of the end caps (16, 20), the short cylindrical housing (35) and the long cylindrical housing (15).

[0077] In another embodiment of the present disclosure, the outer walls of the outer tube (2) and the inner tube (3) are sealed detachably to the at least three tube sheets (17, 18, 19) with a plurality of grommets (40). When the outer tube (2) and the inner tube (3) are arranged vertically, the plurality of grommets (40) comprises a plurality of sealing lips (41) to prevent the outer tube (2) and the inner tube (3) from slipping downwards through the plurality of grommets (40). Further, when the outer tube (2) and the inner tube (3) are circular, the plurality of grommets (40) are rotationally symmetrical.

[0078] In a further embodiment of the present disclosure the outer surface of the outer tube (2) and the inner tube (3) is detachably sealed to the atleast three tube sheets (17, 18, 19) with o-rings.

[0079] The effect / apparatus21 illustrates the recirculation of part of the concentrate 7 / 37. The concentrate (7) flows at position K from the interior of the lower end cap 20 to the pump 36. The pump 36 conveys the recirculated concentrate 37 into the newly inflowing concentrate 7. The mixture of concentrates 7 and 37 flows into the short cylindrical housing 35 at position J and is distributed to the two concentric annular gaps 4 shown here in each set of apparatus.further illustrates that the atleast three tube sheets are installed between the flanges of the caps, the short cylindrical housing and the long cylindrical housing

[0080] Referring to, illustrates the cross-sectional view of rotationally symmetrical grommets, in accordance with an embodiment of the present disclosure. In particularillustrates two versions of grommets configured for detachably sealing the outer walls of the tubes 2 and tubes 3 to the at least three tube sheets. Both versions of grommets are 360degrees rotationally symmetrical and comprises of plurality of sealing lips 41. The horizontal tube sheet is positioned outwards between the extensions 38 and 39.

[0081] The above description along with the accompanying drawings is intended to disclose and describe the preferred embodiments of the invention in sufficient detail to enable those skilled in the art to practice the invention. It should not be interpreted as limiting the scope of the invention. Those skilled in the art to which the invention relates will appreciate that many variations of the exemplary implementations and other implementations exist within the scope of the claimed invention. Various changes in the form and detail may be made therein without departing from its spirit and scope. Similarly, various aspects of the present invention may be advantageously practiced by incorporating all features or certain sub-combinations of the features.

Claims

A tube-in-tube assembly (1) for an integrated condensation and evaporation unit, comprising:an outer tube (2) andan inner tube (3);wherein a portion of the inner tube (3) is concentrically positioned within a portion of the outer tube (2) along a vertical axis of the outer tube (2) thereby forming a concentric annular gap (4) between an inner surface of the outer tube (2) and an outer surface of the inner tube (3).The assembly (1) as claimed in claim 1, wherein the outer tube (2) is fabricated with a high thermal conductivity material selected from one of polymer Polyvinylenesulphide (PPS) filled with graphite (Gr) in the range of 55% to 85% by mass, polymer Polypropylene (PP) filled with graphite (Gr) in the range of 50% to 85 % by mass.The assembly (1) as claimed in claim 2, wherein the outer tube (2) is fabricated with the polymer Polyvinylenesulphide (PPS) filled with graphite (Gr) is resistant to continuous temperature in the range 90°C to 200°C.The assembly (1) as claimed in claim 2, wherein the outer tube (2) is fabricated with the polymer Polypropylene (PP) filled with graphite (Gr) is resistant to continuous temperature in the range 1 to 100°C.The assembly (1) as claimed in claim 1, wherein the inner tube (3) is fabricated with a low thermal conductivity material selected from a group comprising of unfilled polymers Polyvinylenesulphide (PPS), Polypropylene (PP).The assembly (1) as claimed in claim 1, wherein the outer tube (2) and inner tube (3) has a length in the range of 1000mm to 3000mm.The assembly (1) as claimed in claim 1, wherein the outer tube (2) comprises of a plurality of fins in the axial direction.The assembly (1) as claimed in claim 1, wherein the inner tube (3) comprises of a plurality of positioning aids for maintaining the concentric annular gap (4) between the outer tube (2) and the inner tube (3).The assembly (1) as claimed in claim 1, wherein the shape of the outer tube and the inner tube is selected from one of circle, oval, rectangle.An apparatus (21) for integrated condensation and evaporation, comprising:a housing (5) arranged to secure at least two tube-in-tube assemblies (1a, 1b), each comprising an outer tube (2) and an inner tube (3);at least three tube sheets (17, 18, 19) positioned between the at least two tube-in-tube assemblies (1a, 1b); anda plurality of inlets and outlets;wherein a portion of the inner tube (3) is concentrically positioned within a portion of the outer tube (2) along the vertical axis of the outer tube (2) thereby forming a concentric annular gap (4) between an inner surface of the outer tube (2) and an outer surface of the inner tube (3).The apparatus (21) as claimed in claim 10, wherein the housing (5) comprises a vertical section from bottom to top comprising a first end cap (16), a short cylindrical part (35), a long cylindrical part (15) and a second end cap (20).The apparatus (21) as claimed in claim 11, wherein the first end cap (16), the second end cap (20), the short cylindrical part (35) and the long cylindrical part (15), each comprises at least one flange.The apparatus (21) as claimed in claim 10, wherein the outer walls of the outer tube (2) and the inner tube (3) are sealed detachably to the at least three tube sheets (17, 18, 19) with a plurality of grommets (40) and o- rings.The apparatus (21) as claimed in claim 13, wherein the plurality of the grommets (40) comprises a plurality of sealing lips (41).The apparatus (21) as claimed in claim 10, wherein the at least three tube sheets (17, 18, 19) are fabricated with high performance polymer selected from one of Polyvinylenesulphide (PPS), Polypropylene (PP), filled with glass fiber in a range of 40% to 85% by weight.The apparatus (21) as claimed in claim 10, wherein the housing (5) is fabricated with a material selected from glass fiber reinforced Polyvinylenesulphide (PPS), glass fiber reinforced Polypropylene (PP), steel that is protected against corrosion on the inside with a layer of plastic, enamel.The apparatus (21) as claimed in claim 10, wherein the plurality of the inlets comprises of a feed inlet, a vapour inlet and a distillate inlet.The apparatus (21) as claimed in claim 10, wherein the plurality of outlets comprises of a feed outlet, a vapour outlet and a distillate outlet.A system (100) for integrated condensation and evaporation, comprising:at least two apparatuses (21, 22), wherein the at least two apparatuses (21, 22) are connected in series via at least one connecting pipe (24, 25, 27), configured to transfer a vapour (6, 9), a distillate (13) and a concentrate (7) from one apparatus to another;wherein the each apparatus (21, 22) comprises:a housing (5) arranged to secure at least two tube-in-tube assemblies (1a, 1b) comprising an outer tube (2) and an inner tube (3);at least three tube sheets (17, 18, 19) positioned between the at least two tube-in-tube assemblies (1a, 1b); anda plurality of inlets and outlets;wherein a portion of the inner tube (3) is concentrically positioned within a portion of the outer tube (2) along the vertical axis of the outer tube (2) thereby forming a concentric annular gap (4) between an inner surface of the outer tube (2) and an outer surface of the inner tube (3).The system (100) as claimed in claim 19, wherein the at least one connecting pipe (25) comprises a throttle (26).The system (100) as claimed in claim 19, wherein the at least one connecting pipe (27) comprises a vapor generator (28).The system (100) as claimed in claim 19, wherein the operating temperature of the system (100) is in the range of 35 ℃ to 200℃.A method for integrated evaporation and condensation, the method comprising the steps of:passing a first vapor (6) in a first apparatus (21) through at least one tube in tube assembly (1) at a vapor inlet, into an interior of a long cylindrical part (15) of a housing (5) followed by condensing the first vapor (6) on the outer surface (12) of an outer tube (2) and forming a distillate (13);transferring the condensation energy released by condensation of the first vapor (6) through the outer surface (12) of the outer tube (2) to the distillate (13) flowing downwards;collecting the distillate (13) on the upper surface (14) of the second tube sheet (18) in a vertical direction from the top of the tube in tube assembly (1);passing a concentrate (7) through a concentric annular gap at positions C and D and the concentrate (7) enters the concentric annular gap (4) at position E;flashing the concentrate (7) through the lower pressure in the concentric annular gap (4), subsequently flowing of concentrate (7) through the throttle (8);passing a feed mixture of a second vapor (9) and concentrate (7) upward into the tubes (2) with the larger diameter within the annular gap (4) at the position E between the outer tube (2) and inner tube (3), wherein the feed mixture flashes due to the transferred condensation energy and lower absolute pressure in the annular gap (4) and inside the first end cap (16);separating the second vapor (9) and concentrate (7) at the upper end G of the concentric annular gap (4);wherein the concentrate flows downward in the interior (10) of the inner tube (3) at position G due to gravity and lower pressure in the interior (10) of the inner tube (3);wherein the concentrate (7) flows into the inner volume of the lower end cap (20) at the lower end of the inner tube (3); andwherein the concentrate (7) flows out of the lower end cap (20) at position H through the outlet opening to the next effect or to the concentrate tank (29).The method as claimed in claim 23, wherein the vapor (9) flows from the top of the tubes (2) with the larger diameter into the interior of the upper end cap (16) and then through the outlet opening into the second apparatus (22).

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